Apparatuses such as divergent antennae that are made of conventional materials can diverge electromagnetic waves, but have the following shortcomings: the volume thereof is bulky, which is unfavorable for miniaturization; they rely on the shape thereof heavily, which makes it difficult to design these apparatuses flexibly; and they suffer from a considerable loss and the media used are liable to aging, so the cost is high.
Nowadays, metamaterials are receiving increasing attention as a kind of new materials. The metamaterials refer to man-made composite structures or composite materials having supernormal physical properties that natural materials lack. Through structurally ordered design of critical physical dimensions of the materials, restrictions of some apparent natural laws can be overcome to obtain supernormal material functions that natural materials lack.
“Metamaterials” that have been developed so far include “left-handed materials”, “photonic crystals”, “meta-magnetic materials” and the like. Properties of the metamaterials are usually not primarily determined by intrinsic properties of the constitutional material, but by the man-made structures formed therein.
In order to achieve divergence of an electromagnetic wave, the following indicators among others must be satisfied:
1) High performance. The electromagnetic wave shall be diverged at high performances to approximate the desired divergence state.
2) Low loss. Energy of the electromagnetic wave shall be diverged at a high diverging efficiency to achieve the goal of energy saving.
3) Small dimensions. That is, the apparatuses shall not occupy a large space.
Furthermore, the method of diverging the electromagnetic wave shall be easy to be implemented without a complex design, and the cost of components shall not be too high.